Previous reports from this laboratory have demonstrated a technique for culturing feline parotid acinar cells on collagen gels. Feline acinar cell cultures have been assayed from cell viability by: 1. Exclusion of vital dyes; 2. Light and electron microscopy to determine morphology; 3. Cellular growth determined through formation of monolayers and by DNA assays; and 4. Lack of amylase release into the culturing medium without stimulation. Viral infection with feline rhinotracheitis, a herpes virus, has been correlated with indirect fluorescent antibody procedures, cyclic AMP and GMP measurements, and potential measurements. The results of these studies indicate that 18-24 hours post-infection with herpes virus, cells demonstrate ballooning of the nucleus and regions of thickening in nuclear membranes. In addition, presence of viruses is noted in electron microscopic observations. Infected cells also show membrane potential measurements which are significantly less negative than those found in control cultured cells (X control cells equals -50.8 plus or minus 6.8; X virally infected cells equals -18.9 plus or minus 7.9 S. D. mV), and cyclic AMP measurements which are also less than found in control cells (X control cells equals 5.5 plus or minus 1.2; X virally infected cells equals 4.2 plus or minus 1.0 S. D. pmoles CAMP per 10 to the 6th power cells). The physiologic mechanisms underlying these changes will be examined.